Selective Catalytic Reduction (SCR) systems inject AdBlue (urea solution) into the exhaust stream, where it converts harmful NOx into nitrogen and water vapor. SCR is essential for meeting Euro 6 and later emissions standards.
Обзор
AdBlue is injected upstream of the SCR catalyst. Heat converts urea to ammonia, which reacts with NOx on the catalyst surface. The ECU precisely controls dosing based on NOx sensors and temperature.
Controlled Signals
- AdBlue dosing unit
- NOx sensors (pre and post SCR)
- SCR catalyst temperature
- AdBlue tank level and quality
- Exhaust gas temperature
Maps Involved
- AdBlue Dosing Maps vs exhaust flow/NOx
- SCR Efficiency Maps
- Temperature Activation Maps
- NOx Target Maps
Logic Sequence
NOx Sensor Input → Required Reduction Calculation
↓
SCR Temperature Check (must be >200°C)
↓
AdBlue Dosing Command
↓
Post-SCR NOx Verification
↓
Efficiency Monitoring
Calibration Objectives
- Maximize NOx conversion efficiency
- Minimize AdBlue consumption
- Prevent ammonia slip
Calibration Strategy
- SCR delete requires extensive ECU modification
- Verify NOx sensor calibration after any changes
- AdBlue quality affects system performance
Диагностика
- NOx efficiency below threshold
- AdBlue dosing faults
- SCR catalyst temperature faults
- AdBlue quality/contamination detected
Best Practices
- SCR deletion is illegal for road use
- Use only ISO 22241-compliant AdBlue
- Keep AdBlue tank above minimum level to prevent pump damage